Photographic silver halide emulsions



United States Patent New Jersey No Drawing. Filed Aug. 19, 1963, Ser. No. 303,146 20 Claims. (til. 96-107) This application is a continuation-in-part of my copending application U.S. Serial No. 254,499, filed January 28, 1963, now abandoned, which in turn is a continuation-in-part of US. Serial No. 128,378, filed August 1, 1961, now abandoned.

The present invention relates to photography, and more particularly to light-developable or direct-print photographic silver halide emulsions.

Radiation-sensitive papers adapted for light recording, e.g., oscillographic recording, are known. Typical of such papers are the developing-out and print-out type. The developing-out type, as the name implies, requires that the exposed material be chemically developed, fixed and washed in order to provide a stable visible image on said material. The print-out type of material develops on exposure and requires no development step. The print-out type is generally much slower than the developing-out type and the images are unstable and have a short life.

A third type of radiation-sensitive material especially suitable for light-writing and oscillographic recording comprises a hydrophilic colloid-silver halide emulsion layer which, when exposed to a high intensity source of electromagnetic radiation, forms a latent image which can then be developed by subsequent general exposure to a second source of radiation of lower intensity. Such directwriting or direct-print emulsions are faster than print-out emulsions and require no chemical development. However, many of the recording papers of this third type have a slow rate of photodevelopment and the background areas tend to build up to obscure the image on subsequent exposure to light.

It is an object of this invention to provide a new class of light-developable, direct-print, radiation-sensitive silver halide emulsions.

It is another object of this invention to provide novel photographic silver halide emulsions suitable for preparing direct-print recording paper having a high rate of photodeveloprnent.

It is another object of this invention to provide novel photographic light-developable, direct-print silver halide emulsions that can be chemically developed and fixed before or after photodevelopment to make archival-quality records.

It is another object of this invention to provide new photodevelopable photographic silver halide emulsions that are characterized as having an improved density differential between the initially-exposed and unexposed areas upon photodeveloprnent.

It is also an object of this invention to provide new photodevelopable photographic silver halide emulsions that have improved resistance in the initially-unexposed areas to density increase upon photodeveloprnent and subsequent exposure to light.

These and other objects of the invention are accomplished by incorporating into light-developable, directprint, radiation-sensitive silver halide emulsions cupric 3,241,971 Patented Mar. 22, 1966 salts and heterocyclic and/ or aromatic thione or mercaptan halogen acceptors. The invention also includes the use of substituted thiourea halogen acceptors and watersoluble iodides in light-developable, direct-print, radiation-sensitive silver halide emulsions, with or without cupric salts.

A wide variety of mercaptans or thiones having a mercapto group (SH) or a thione group 8) attached to a heterocyclic nucleus can be utilized in the emulsions of the invention. Useful heterocyclic mercaptans or thiones have at least one mercapto or thione group attached to a cyclic nucleus having at least one, and more generally 1 to 4, nitrogen atoms. Such heterocyclic mercaptans and thiones can contain other hetero-atoms in addition to hetero-nitrogen atoms such as hetero-oxygen atoms and hetero-sulfur atoms. Typical useful heterocyclic mercaptans and thiones include mercaptotetrazoles, rnercaptothiazoles, mercaptoimidazoles, mercaptotriazolotriazoles, mercaptoazaindenes, mercaptothiadiazines, mercaptothiadiazoles, mercaptopiperazines, mercaptobenzoxazoles, mercaptooxazolidines, mercaptobenzimidazoles, oxazoline-thiols, mercaptotriazines, mercaptotriazoles, mercaptodiazanaphthalenes and other well-known heterocyclic mercaptans. Preferred heterocyclic mercaptans are those that form substantially water-insoluble silver salts. Illustrative heterocyclic mercaptan and thione halogen acceptors of the invention include S-amino-Z-mercapto- 1 ,3 ,4-thiadiazole,

l-methyl-2-mercaptoimidazole,

1,4-bis Z-mercaptoethy-l piperazine,

1- Z-diethylaminoethyl) l ,2,5 ,6-tetrahydro- 1 ,3 ,5-

triazine-4-thiol,

Z-irnidazoline-thione,

1,3 -dimethyl-2-imidazoline-thione,

l-methyl-2-imidazole-thione,

2-meroaptobenzoxazole,

Z-rnercaptobenzimidazole,

Oxazoline-Z-thiol,

S-mercapto-S-methyll ,2,4-triazole,

3-mercaptol ,2,3 a-triazaindene,

4-merca-pto-1,2,3-triazanaphthalene,

3-mercapto-1,2,4-triazole,

S-acetamido-l,3,4-thiodiazole-2-thiol S-acetamido-Z-mercapto-thiazole,

S-p-chlorophenyl-Z-mercaptol ,3 ,4,4H-thiadiazine,

5,6-di-methyl-3-mercapto-1,2,4-triazabenzene,

4,5 -diamino-2-mercaptopyrimidine,

6-hydroxy-3 -mercapto-5-methyl-1,2,3 a,4,7-pentazaindene,

7-methyl-6-thiopurine,

l-m-carboxyphenyl-S-mercaptotetrazole,

1- 3-methylsulfonamido -phenyl-5-mercaptotetrazole,

2-mercapto-4-phenylthiazole,

1-phenyl-S-mercaptotetrazole,

1-isoarnyl-Z-mercaptoimidazole,

2,4-dimercapto-6-phenyldihydro-S-triazine,

4-mercapto-6-methyl-l,3,3a,7-tetraazaindene,

1- {3 a- (2,4-di-t-amylphenoxy) acetamido] -phenyl}-5- mercaptotetrazole,

3-benzamido-4-benzoyl-5-rnercapto-1,2,4-triazole hemihydrazine salt,

2-mercapto5-methyl-4H,1,3 ,4-thiadiazine,

2-mercapto-5-phenyl-4H,l,3,4-thiadiazine,

Tri-thiocyanuric acid,

3 1-n-butyl-1,2,3 ,6-tetrahydro- 1,3 ,5 -triazine-4-thiol, 1-0 ctyll ,2,3 ,6-tetrahydrol ,3 ,5-triazine-4-thiol, 3 ',5-dimercapto-3 ,5 -diphenyldihydro-1,2-triazolo-triazole, 1,2-bis(1,2,5,6-tetrahydro-1,3 ,5 -triazine-4-thiol) ethane, 4,5-diphenyl-2-imidazolinethione, 2-imidazole-thione, Z-thiouracil, 4-thiobarbituric acid, 4,5 1,2-D-fiucofurano -2-oxazolidine thione, 4,5 -diphenyl-2-imidazoline-thione, Z-mercapto-S-phenylbenzoxazole, 4-mercapto- 1 ,3 -diazanaphthalene, 3 -mercapto-8-oxal ,2,3 a-triaza-cyclopent a] indene, and 2-mercapto-naphth-[1,2]-oxazole.

Useful aromatic mercaptan halogen acceptors are mercaptans having at least one mercapto group attached to an aromatic nucleus such as a benzene or a naphthalene nucleus. Useful aromatic mercaptan halogen acceptors include thiosalicylic acid, Z-naphthalenethiol, benzenethiol and the like.

A particularly useful class of mercaptans or thiols that can be utilized in the emulsions of the invention with or without cupric salts are substituted thiourea halogen acceptors. Typical suitable substituted thioureas have the structure.

wherein:

R and R can be hydrogen atoms, alkyl groups and including substituted alkyl groups, aryl groups such as those of the naphthyl and phenyl series, acyl groups wherein R can be an alkyl or an aryl group such as those of the naphthyl and aryl series, and together the necessary atoms to make a heterocyclic nucleus with the thiourea structure to form such cyclic compounds as a triazolethiol, an imidazolethione, an imidazoline-thione, a triazine-thiol, a thiobarbituric acid, a thiouracil or the like cyclic thioureas and including such substituents as alkyl groups and aryl groups such as those of the naphthyl and phenyl series; R and R can be hydrogen atoms, alkyl groups and including substituted alkyl groups, aryl groups such as those of the naphthyl and phenyl series, and acyl groups it C Rs described above; at least one of R R ,R and R being other than a hydrogen atom. The alkyl substituents for the described substituted thioureas can be widely varied, and typically have 1 to 18 carbon atoms and preferably 1 to 8 carbon atoms.

Typical suitable substituted thioureas are set out above in the list of heterocyclic mercaptans and thiones. Other suitable substituted ureas include:

Tetramethylthiourea, l-isopentyl-2-thiourea, l-phenyl-Z-thiourea, 1,3-diphenyl thiourea, 1-acetyl-2-thiourea, 1,3-dibenzylthiourea, 1,1-diphenyl-2-thiourea, l-ethyll tat-naphthyl -2-thiourea, and 1-(o-methoxyphenyl)-2-thiourea.

The concentration of mercaptan and thione halogen acceptors utilized in the emulsions of the invention can be widely varied, amounts in excess of those generally utilized for antifoggant purposes in conventional developing-out emulsions being utilized in the present instance. Generally about .1 to 50 mole percent, and preferably about 1 to 10 mole percent, based on the silver halide in the emulsion of the heterocyclic mercaptan or the aromatic mercaptan is utilized.

As described above, copper salts can be used in the emulsions of the invention. Typical cupric salts are cupric acetate, cupric sulfate, cupric nitrate, and the like. Cupric salts that can be readily incorporated into photographic emulsions in accordance with usual practice are utilized. Hence, water-soluble salts and salts soluble in water-miscible solvents such as methanol, ethanol and the like are generally used. The amount of cupric salt utilized can be widely varied, although amounts of about .5 to mole percent, and preferably about 1 to 20 mole percent, based on the silver halide are utilized.

Although silver halide emulsions are generally made with an equivalent or slight excess of halide ion present, I have found it desirable to add additional water-soluble iodide to the silver halide emulsion after its precipitation but before it is coated More generally, about .1 to 50 mole percent, and preferably about 1 to 10 mole percent of water-soluble iodide based on the silver halide in the emulsion is used. Illustrative water-soluble iodides include ammonium, calcium, lithium, magnesium, potassium, or sodium iodide.

A wide variety of light-developable photographic silver halide emulsions can be utilized in the invention, such being well known to those skilled in the art. Suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, and silver chlorobromoiodide. For a description of suitable emulsions, reference is made to Davey et al., U.S. Patent 2,592,250, issued April 8, 1952; Glafkides, Photographic Chemistry, vol. 1, pp. 31-2, Fountain Press, London; and McBride application Serial No. 222,964, filed September 11, 1962, wherein is disclosed the preparation of silver halide emulsions in the presence of thioethers such as 3,6-dithia-1,8-octanediol, 1,l0-dithia-4,7,13,l6-tetraoxacyclooctadecane, 7,10- diaza 1,16 dicarboxamido-3,14-dithiahexadecane-6,11- dione, and 1,17-di-(N-ethylcarbamyl)-6,12-dithia-9-oxaheptadecane. The present silver halide emulsions generally have an average grain size of about .1 to 10 microns, and more generally about .5 to 1 micron.

The so-called internal image emulsions are particularly useful in the invention, such emulsions comprismg silver halide grains having a substantial amount, and preferably a predominant amount, of sensitivity internal to the grain. Typically, such internal image emulsions are those which, when measured according to normal photographic techniques by coating 21 test portion of the emulsion on a transparent support, exposing to a light intensity scale having a fixed time between 1 10- and 1 second, bleaching 5 minutes in a 0.3% potassium fern'cyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B below (an internal-type developer), have a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A below (a surface-type developer).

Water to make 1 liter.

E3 DEVELOPER B N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Sodium thiosulfate 10.0

Water to make 1 liter.

A large variety of hydrophilic, water-permeable organic colloids can be suitably utilized in preparing the silver halide emulsions or dispersions of the invention. Gelatin is preferably utilized although other colloidal material such as colloidal albumin, cellulose derivatives, synthetic resins or the like can be utilized. Suitable colloids that can be used are polyvinyl alcohol or. a hydrolyzed polyvinyl acetate as described in Lowe, US. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19 to 26% as described in US. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy, US. Patent 2,322, 085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 30 to 60% and a specific viscosity of 0.25 to 1.5 on an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon, US. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe, US. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith, US. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest, US. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in Illingsworth, Dann and Gates, US. Patent 2,852,382, issued September 19, 1958.

The subject photodevelopable photographic silver halide emulsions of the invention can contain the addenda generally utilized in such products including gelatin hardeners, gelatin plasticizers, coating aids and the like.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include paper, cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related fims of resinous materials and others.

In forming a photodeveloped image with a typical photographic element containing an emulsion of the invention, the photographic element is initially exposed to a high intensity source of electromagnetic radiation such as a high intensity light source rich in blue and ultraviolet light such as are used in oscillographs described in Heiland, U.S. Patent 2,580,427, issued January 1, 1952, high intensity visible light, X-radiation and the like, to form a latent image in the emulsion of the photographic element, and thereafter the resulting latent image is photodeveloped by overall exposure of the emulsion to a radiation source of less intensity than the original exposure, such as to a convention fiuoroescent light, light from incandescent lamps commonly used for general illumination, or even ordinary daylight. Generally, the latent image formed in the emulsion in the first instance is not visible and does not become visible until photodevelopment. Heat is desirably utilized during the photodevelopment step. Typically the subject emulsions are heated to a temperature of about 90 C. to 200 C. for about 1 to 30 seconds and photodeveloped after the initial high intensity exposure.

If desired, photographic elements containing the emulsions of the invention can be developed and fixed in aqueous chemical developing-out and fixing solutions after the initial exposure forming the latent image, or after the above-described photodevelopment. The substituted thiourea halogen acceptors described above have particular utility with respect to this feature as they can be chemically developed and fixed before or after photodevelopment to make archival-quality records.

Example 1 A gelatino-silver chlorobromoiodide direct-print emulsion having high internal sensitivity and low surface sensitivity was prepared by the method described in Davey at al., US. Patent 2,592,250. To separate portions of this emulsion were added various combinations of the invention and thereafter coated on a photographic paper support at a coverage of mg. of silver per square foot and 280 mg. of gelatin per square foot. The feature addenda of the invention were added as solutions, for example, a methanol solution of the mercaptan was added to the emulsion with rapid stirring followed by the addition of a water solution of potassium iodide to yield 2 mole percent of iodide based on the silver halide followed by the addition of a water solution of the copper salts with rapid stirring just prior to coating on the paper support. Summarizing below, are seven combinations of emulsion addenda of the invention that were incorporated in the described emulsion, the amounts indicated below being in terms of grams per mole of silver halide:

(1) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams of thiosalicylic acid,

(2) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams 1 (3 methylsulfonamido)phenyl-S-mercaptotetrazole,

(3) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams Z-mercapto-4-phenylthiazole,

(4) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams l-isoamyl-2-mercaptoimidazole,

(5) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams l-m-carboxyphenyl-S-mercaptotetrazole,

(6) 26.2 grams cupric sulfate pentahydrate plus 6.1 grams 2,4-dimercapto-6-phenyldihydro-s-triazine, and

(7) 26.2 grams cupric sulfate pentahydrate plus 6.1

grams 4-mercapto-6-methyl-1,3,3a,7-tetraazaindene.

A sample of each of the above coatings was exposed initially on a Heiland 906B oscillograph, which oscillograph has a high intensity light source rich in ultraviolet light.

The exposed samples were thereafter photodeveloped by exposure to approximately 1000-foot candles of white fluorescent light for approximately 5 seconds. In each instance the exposed and photodeveloped samples produced substantially higher densities in the initially exposed areas and lower densities in the unexposed background areas than produced in control coatings containing the copper sulfate alone, the mercaptan alone, or

a control coating free of the mercaptan and the copper salt. In each sample coating of the invention, the exposed areas reached maximum density substantially faster when photodeveloped than samples not containing the combinations of the invention.

Example 2 Several portions of an emulsion of the type described in Example 1 were tested containing varying amounts of a combination of a mercaptan and a copper salt, more specifically, concentrations of 1-phenyl-5-mercaptotetrazole ranging from 3.4 to 13.4 grams per mole of silver halide in combination with cupric sulfate pentahydrate at concentrations ranging from 9.4 to 38.4 grams per mole of silver halide in the emulsion were tested. When exposed and photodeveloped as described in Example 1, excellent contrast, high density in the initially-exposed areas, and low density in the background areas were obtained in all cases.

7' Example 3 A light-developable, direct-print, light sensitive gelatino-silver chlorobromoiodide emulsion having high internal sensitivity and low surface sensitivity was prepared mercaptan per mole of silver. An emulsion portion without the heterocyclic mercaptan was also prepared as a control for comparative purposes. The emulsions were coated on a photographic paper support at coverages of 111 mg. of silver and 254 mg. of gelatin per square foot.

y the method descflbcd 1n QY et en The various coated samples were than exposed through N To separate p p f th1s emulslon a 0.15 log E neutral density step tablet for second were added various addenda of the invention and thereon an Edger-ton, Germeshausen and Grier Mark VI senafter coated on a photographic paper support at a coversitometer. The exposed samples were then photodevele f 110 Silver P Square foot and 255 gof oped by exposing for 5 minues to a 60 foot-candle coolgelatin per square foot. Portions of the emulsion conwhite fluorescent light source. All of the exposed and TABLE I AD for var in hot (1 l l Emulsion Feature addenda and concentration in mole y g p 0 We opment exposures Got candle mmutcs) N 0. percent based on the silver halide Control 01 .02 -.02 02 01 0 0 0 1-n-b7utyl-1,2,3,0tetrahydro-1,3,5 triazine-4-thiol 05 08 07 07 07 07 04 0 Potassium iodide (00). .04 .11 .18 .26 1 .24 Thiosalicyclic acid (1.4) .02 06 10 18 5 20 Cupric sulfate 10. 02 03 01 0 02 .04 03 02 Addenda of Emulsion Nos. 2 and 5... 13 20 29 38 .32 12 04 Addenda of Emulsion Nos. 4 and 5.. 17 .20 27 32 39 .37 12 I 05 Addenda of Emulsion Nos. 2, 4 and 5- 23 .32 .44 .40 .48 .35 I14 I03 Addenda oi Emulsion Nos. 2, 3, 4 and 5 33 .45 .53 36 .13 05 taining no feature addenda were also coated in a similar manner for comparative purposes. The various coatings were then exposed initially on a Heiland Strobonar lamp, :1 high intensity light source rich in ultraviolet light, for 500 microseconds. The exposed samples were than photodeveloped by exposure to 2000 foot-candles for 30 minutes through a step tablet containing steps with a successively increasing density of approximately 0.5 log E. The first step (clear, containing no density) allowed 60,000 foot-candle minutes of light to strike the test samples in that area, the second step (0.5 log E density) modulated this exposure so that the effective exposure was only 16,900 foot-candle minutes, etc. The densities obtained were read on each step for the image and background areas through a Wratten No. 15 filter on a Kodak curve-tracing densitometer. All of the density measurements were made under safelight so that the densities did not change under these measurements. Summarized above in Table I are the differences in densities between the image and background areas (AD). The coatings with the greatest stability are the coatings which retain the highest degree of differentiation (AD) over the longest exposure value range.

As can be observed from the data set out in Table I above, the cupric salt and the heterocyclic mercaptan and/or the aromatic mercaptan, as Well as the iodide salt, cooperate in internal image silver halide emulsions to give useful direct-print coatings. The high AD values for the emulsions containing the addenda of the invention indicate the substantial differences between background and image densities of such emulsions resulting on high intensity exposure and photodevelopment in the usual manner. The high AD values at the left portion of the table (e.g., at 60,000 foot-candle minute photodevelopments) are indicative of the resistance to fading that characterizes direct-print products prepared with the emulsions of the invention.

Example 4 A gelatino-silver chlorobromide emulsion having high internal sensitivity and low surface sensitivity was prepared by the method described in Davey et al., US. Patent 2,592,250. The prepared emulsion was split into several portions, each portion containing 0.01 mole of thiosalicylic acid, 0.10 mole of cupric sulfate, 0.02 mole of potassium iodide, and 0.03 mole of a heterocyclic photodeveloped samples had substantially higher densities in the image areas than in the background areas and relatively high speeds. Table II below sets out the relative speeds for the various test coatings.

TABLE II Relative Heterocyclic mercaptan addenda: speed Control 1 {3 [a (2,4-di-t-amylphenoxy)acetamido]- phenyl}-5-mercaptotetrazole 300 3-benzamido-4-benzoyl 5 mercapto-1,2,4-

triazolehemihydrazine salt 600 2-mercapto-5-methyl-4H,1,3,4-thiadiazine 300 2-mercapto-5-phenyl-4H,1,3,4-thiadiazine S-p-chlorophenyl 2 mercapto-4H,1,3,4-thiadiazine 150 Tri-thiocyanuric acid 300 2-mercapto-S-phenylbenzoxazole 1800 l-octyl 1,2,3,6 tetrahydro-l,3,5-triazine-4- thiol 1200 3,5 dimercapto 3,5 diphenyldihydro-1,2-

triazolotriazole 300 4,5 (1,2 D glucofurano)-2-oxazolidinethione 1200 4,5 (2,3 D fructopyrano) 2 oxazolidinethione 300 2-mercaptobenzoxazole 600 Z-mercaptobenzimidazole 1200 4-mercapto-1,S-diazanaphthalene 300 3 mercapto 8 oxa-1,2,3-triazo-cyclopent- [a]indene 150 2-mercapto-naphth-[1,2]-oxazole 1800 The data in Table 2 illustrates the increased speeds that result when heterocyclic mercaptans are added to the present emulsions containing a cupric salt, an aromatic mercaptan and a water-soluble iodide salt.

Example 5 The photographic coatings described in Example 1 were exposed initially on a Consolidated Electrodynamics Corp. Model 5-123 oscillograph which has a light source of ultraviolet light. The exposed samples were photodeveloped for three seconds using an exposure of approximately 1000 footcandles of a white fluorescent light with the back of the paper held in contact with the heat platen of the oscillograph which was maintained at about 107 C. The samples exhibited higher density differential between the image and background areas than did the control coating which was exposed and photodeveloped under the same exposure conditions but in the absence of heat.

Example 6 The coatings described in Example 4 were exposed on a Consolidated Electrodynamics Corp. Model 5-123 oscillograph and photodeveloped in the presence of heat for two seconds with a 1000 foot-candle of a white fluorescent light source, and the temperature of the heat platen maintained at about 107 C. The exposed samples which were photodeveloped in the presence of heat exhibited a higher density and an improved image differentiation over the control sample of Example 4 which was exposed and photodeveloped under the same exposure conditions but in the absence of heat.

Example 7 A light-devolpable, direct-print, light-sensitive gelatino-silver chlorob-romoiodide emulsion (95% bromide, 3% iodide, 2% chloride) having high internal sensitivity and low surface sensitivity was prepared by slowly adding silver nitrate to an aqueous gelatin solution containing a stoichiometric excess of potassium iodide, potassium bromide and potassium chloride to provide a large-grain emulsion. The emulsion was washed with water to remove water-soluble salts. To separate portions of this emulsion were added various addenda of the invention and thereafter coated on a photographic paper support at a coverage of 110 mg. of silver per square foot and 255 mg. of gelatin per square foot. Portions of the emulsion containing no feature addenda were also coated in a similar manner for comparative purposes. The various coatings were then exposed initially on a Heiland Strobnar lamp, a high intensity light source rich in ultraviolet light, for 500 microseconds. The exposed samples were then photodeveloped by exposure to 2000 foot-candles for 30 minutes through a step tablet containing steps with a successively increasing density of approximately 0.5 log E. The first step allowed 4,750 foot-candle minutes of light to strike the test samples in that area, the second step (0.5 log E density) modulated this exposure so that the effective exposure was only 1,500 foot-candle minutes, etc. The densities obtained were read on each step for the image and background areas through a Wratten No. 15 filter on a Kodak curve-tracing densitometer. All of the density measurements were made under safelight so that the densities did not change under these measurements. Summarized below in Table III are the differences in densities between the image and background areas (AD). The coatings with the greatest stability are the coatings which retain the highest degree of differentiation (AD) over the longest exposure value range.

TABLE III l0 visible 0.15 steps when exposed to a 100 microsecond flash on an Edgerton, Germeshausen and Grier Mark VI sensitometer through a 0.15 log E neutral density step tablet followed by a photodevelopment of 5 minutes of foot-candle cool-white fluorescent light.

Example 8 A gelatino-silver chlorobromide direct-print emulsion bromide, 5% chloride) having high internal sensitivity and low surface sensitivity was prepared by slowly adding silver nitrate to an aqueous gelatin solution containing a stoichiometric excess of potassium chloride and potassium bromide to provide a large-grain emulsion.- The emulsion was washed with water to remove watersoluble salts. To separate portions of this emulsion were added typical feature addenda of the invention and thereafter coated on photographic paper supports at coverages of mg. of silver per square foot and 255 mg. of gelatin per square foot. Summarized below in Table IV are the addenda utilized in the prepared emulsions. In Table IV:

Compound I=1-n-butyl-1,2,5,6 tetrahydro-l,3,5 triazine-4-thiol Compound II=potassium iodide TABLE Iv Coating No. Feature addenda and concentration in mole percent based on the silver halide 1 Control.

3.7 mole percent Compound I.

2.1 mole percent Compound II.

3.7 mole percent Compound I plus 2.1 mole percent Compound II.

Several portions of a light-developable, direct-print, light-sensitive gelatino-silver chlorobromide emulsion of the type described in Example 8 were prepared containing various addenda of the invention as described in Table V below and coated on paper supports at coverages of 258 mg. of silver per square foot and 560 mg. of gelatin per square foot. The coatings were exposed to a 100 microsecond flash on an Edgerton, Germeshausen and Grier Mark VI sensitometer containing a xenon light source through a 0.15 log E neutral density step tablet Feature addenda and concentration in AD for varying photodevelopment exposures foot'candle minutes) Emulsion No. mole percent based on the silver halide 1 Control -2 02 02 02 0 0 0 2 l-mbutyl-l,2,3,6-tetrahydro-1,3,5-tria- 07 07 07 07 .04 0

zine-Lthiol (3.7). 3 Potassium iodide (6.0) 18 26 31 24 .09 02 4 Addenda of Emulsion Nos. 2 and 3 24 .36 40 30 11 03 As can be noted from the data set out in the above table, a high density differential between the image and background (AD) is obtained when the heterocyclic mercaptan, l-n-butyl-l,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, is used in combination with the water-soluble halide, potassium iodide, reference being made to Emulsion No. 4. A sample containing Emulsion No. 4 of Table III had 13 and thereafter photodeveloped for 5 minutes with a 60 foot-candle, cool-white fluorescent light source. The number of visible 0.15 log E steps obtained for the various coatings is summarized in Table V. Also, the density difference between image and background after the 5 minute photodevelopment was observed for the various coatings, and which density differences are recorded in Table V as AD. In the various coatings the potassium iodide (KI) was used at concentrations of 2.1 mole percent based on the silver halide and the substituted thioureas were used at concentrations of 3.7 mole percent based on the silver halide unless otherwise indicated.

TABLE V Visible 0.15 log E steps on Emulsion addenda exposure and AD photodevclopment (1) KI 15 37 (2) l-rl-bkutyl-l,2,5,6-tctradhydro-1,3,5-triazine- 16 2S 10 (3) 1-n-butyl1,2,5,G-tetrahydro-1,3,5-triazine- 4-tl1io1 plus KI 17 .48 (4) l-n-butyl-l,2,5,6tetrahydr-1 4-thiol (5.8 mole percent) 16 28 (5) tetramethylthiourea plus K 16+ 36 (6) 1,3-dimethyl-2-imidazolinethione plus KL. 17 45 15 41 (8) 4-pheny 1 2,4-triazole plus KL 16+ 39 (9) 2-mcrcaptoi1nidazole plus KI 16+ 41 (10) l-methyl-2-mereapt0imidazole plus KI. 16+ 40 (11) 2-u1ercaptoimidazoline plus KI 17 42 (12) 1-phenyl-Z-mercaptoimidazoline plus KL. 16+ 42 (13) 1,3-diinethyl-2-rnercaptoiinidazoline plus KI 16+ 39 (14) 5,5-diiuethyl-Z-mereaptohydantoin plus 39 15 (15) 4,5-diphenyl-2-mereaptoimidazoline plus 40 16 (16) 1,1-diphenyl-2-thiourea plus KI 15+ 43 (17) 1,3-di-(m-methoxyplicnyl)-2-thiourea plus KI 16 41 (18) 1-(o-inethoxyphenyl)-2-thiourea plus KI. 15+ 45 (19) l-(p-methoxyphenyl)-2-thi0urea plus KL. 16+ 45 (20) 1-1ucthyl-1,2,5,6-tetrahydr0-4-mercapLo-l,

3,5-triazinc plus KI 16 .38 (21) 4-thiobarbituric acid plus KI. 15 44 (22) l-allyl-l-thiourea plus KI... 17 44 (23) 2-thiouracil plus KI 16 38 (24) l-acetyl-Q-thiourca plus K 16+ .45 (25) 1-ethyl-1-(a-naphthyl)-2-thiourca plus KI. 16 (2G) 2-imidazolinethione plus KI 17 .47 (27) l-isopentyl-Z-thiourea plus KI 17 .45 (28) 1-(2-diethylaminoethyl)-1,2,5,6-tetrahydro-4-mcrcapto-1,3,5-triazine plus KI. 17 41 (29) 1,2-bis(1,2,5,6-tdtral1ydro-4-mercaptotriazine)-ethane plus KI 17 42 (30) 4-ethylcarboxyrnctl1yl-l,2,5,6-tetrahydro- 4-rnereapto1,3,5-trizaiue plus KI 17 (31) l-phenyl-Z-thiourea plus KI 17 42 Example 10 Several portions of a light-developablc, direct-print, light-sensitive gelatino-silver chlorobromide emulsion of the type described in Example 8 were prepared containing various addenda as described in Tables VI and VII below and coated on paper supports at coverages of 258 mg. of silver per square foot and 560 mg. of gelatin per square foot. Each of the emulsions contained 1.66 g. of potassium iodide per mole of silver halide and a sulfur-containing compound as indicated in Tables VI and VII in terms based on the silver halide. The coatings described in Table VI were stored for 3 days at 120 F. and 35% relative humidity, and then exposed to a 100 microsecond flash on an Edgerton, Germeshausen and Grier Mark VI sensitometcr containing a xenon light source through a 0.15 log E neutral density step tablet. Some of the exposed coatings were then chemically developed and fixed, while other coatings were photodeveloped for 5 minutes with a 60 foot-candle, cool-white fluorescent light source and then chemically developed and fixed (1 minute chemical development and 1.5 minute fixing at 72 F.). The developer utilized had the formula:

Benzoxazolethiol mg 25. Water .to make 2 liters.

12 The fixing bath utilized had the formula:

Sodium thiosulfate g 2400 Sodium sulfite (anhydrous) g 15.0 Acetic acid, 28% cc 48.0 Boric g 7.5 Potassium alum g 15.0

Water to make one liter.

The number of visible 0.15 log E steps obtained for the various coatings is summarized in Tables VI and VII. Also, the density difference between image and background of the processed coatings was observed and recorded in Tables VI and VII as AD.

As can be observed from the data set out in Tables VI and VII, the present substituted thioureas as defined hereinabove have particular utility as they can be utilized as halogen acceptors in direct-print emulsions that can be effectively chemically developed and fixed before or after photodevelopment to make archival-quality records. Thiourea and thiosemicarbazide are not as useful.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A light-developable, direct-print, radiation-sensitive emulsion comprising silver halide grains, a predominant amount of said radiation sensitivity being internal to said grains, a mercaptan halogen acceptor selected from the group consisting of a compound having at least one mercapto group attached to an aromatic nucleus and a compound having at least one mercapto group attached to a heterocyclic nucleus having at least one heteronitrogen atom, and a cupric salt.

2. A light-developable, direct-print, radiation-sensitive emulsion comprising silver halide grains, a predominant amount of said radiation sensitivity being internal to said grains, a mercaptan halogen acceptor having at least one mercapto group attached to a heterocyclic nucleus having at least one heteronitrogen atom, and a cupric salt.

3. A light-developable, direct-print, radiation-sensitive emulsion comprising silver halide grains, a predominant amount of said radiation sensitivity being internal to said grains, a mercaptan halogen acceptor having at least one mercapto group attached to an aryl nucleus, and a cupric salt.

4. A light-developable, direct-print, radiation-sensitive emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, a hydrophilic colloid, about .1 to mole percent based on said silver halide of a mercaptan halogen acceptor having at least one mercapto group attached to a heterocyclic nucleus having at least one hetero-nitrogen atom, about .5 to 120 mole percent based on said silver halide of a cupric salt, and about .1 to 50 mole percent based on said silver halide of a mercaptan halogen acceptor having at least one mercapto group attached to an aryl nucleus.

5. A light-developable, direct-print, radiation-sensitive emulsion comprising silver halide grains having an average size of about .1 to microns, a predominant amount of the said radiation sensitivity being internal to said grains, a hydrophilic colloid, about .1 to 50 mole percent based on said silver halide of a mercaptan halogen acceptor having at least one mercapto group attached to a heterocyclic nucleus having at least one hetero-nitrogen atom, about .5 to 120 mole percent based on said silver halide of a cupric salt, about .1 to 50 mole percent based on said silver halide of a rnercaptan halogen acceptor having at least one mercapto group attached to an'aryl radical, and about .1 to 50 mole percent based on said silver halide of a Water-soluble iodide.

6. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 .to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .5 to 120 mole percent based on said silver halide of a Water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of a heterocyclic mercaptan halogen acceptor having a mercapto group attached to a cyclic nucleus selected from the group consisting of a triazine nucleus and a tetrazole nucleus, and about .1 to 50 mole percent based on said silver halide of a Water-soluble iodide.

7. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .5 to 120 mole percent based on said sliver halide of a Water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of an aromatic mercaptan halogen acceptor having a mercapto group attached to a benzene nucleus, and about .1 to 50 mole percent based on said silver halide of a Water-soluble iodide.

8. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .5 to 120 mole percent based on said silver halide of a water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of thiosalicylic acid, and about .1 to 50 mole percent based on said silver halide of a water-soluble iodide.

9. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 50 mole percent based on said silver halide of a Water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of 1-phenyl-5-mercaptotetrazole, and about .1 to 50 mole percent based on said silver halide of a Water-soluble iodide.

10. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 50 mole percent based on said sliver halide of a Water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of 1 n butyl l,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, and about .1 to 50 mole percent based on said silver halide of a water-soluble iodide.

11. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about 1 to 20 mole percent based on said silver halide of cupric sulfate, about 1 to 10 mole percent based on said silver halide of thiosalicyclic acid, about 1 to 10 mole percent based on said silver halide of 1 n butyl 1,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, and about 1 to 10 mole percent based on said silver halide of potassium iodide.

12. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .5 to mole percent based on said silver halide of a Water-soluble cupric salt, about .1 to 50 mole percent based on said silver halide of an aromatic mercaptain halogen acceptor having at least one mercapto group attached to a benzene nucleus, about .1 to 50 mole percent based on said silver halide of a mercaptan halogen acceptor having at least one mercapto group attached to a heterocyclic nucleus having 1 to 4 hetero-nitrogen atoms, and about .1 to 50 mole percent based on said silver halide of a water-soluble iodide salt selected from the group consisting of ammonium, calcium, lithium, magnesium, potassium and sodium iodide.

13. A light-developable, direct-print, radiation-sensitive emulsion containing silver halide grains, a predominant amount of said radiation sensitivity being internal to said grains, a Water-soluble iodide and a substituted thiourea halogen acceptor having the formula (A) R and R are each selected from the group consisting of (1) a hydrogen atom, (2) an alkyl group, (3) an acyl group, (4) an aryl group, and (5) together the necessary atoms to complete a heterocyclic nucleus; and (B) R and R are each selected from the group consisting of (1) a hydrogen atom, (2) an alkyl group, (3) an acyl group, and (4) an aryl group; at least one of R R R and R being other than a hydrogen atom.

14. A light-developable, direct-print, radiation-sensitive emulsion containing silver halide grains, a predominant amount of said radiation sensitivity being internal to said grains, a Water-soluble iodide and a substituted thiourea halogen acceptor having the formula R -1\ I-OI \IR wherein:

(A) R and R are each selected from the group consisting of (1) a hydrogen atom, (2) an alkyl group, (3) an acyl group, and (4) an aryl group; and (B) X represents the necessary atoms with the s H No-N- moiety to make a heterocyclic nucleus selected from the group consisting of 1) a triasole-thiol, (2) an imidazole-thione,

1 (3) an imidazoline-thione, (4) a triazine-thiol, (5 a thiobarbituric acid, and (6) a thiouracil.

15. A light-developable, direct-print, radiationsensitive emulsion comprising gelatin, silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 100 mole percent based on said silver halide of water-soluble iodide, and about .1 to 50 mole percent of tetramethylthiourea based on said silver halide.

16. A light-developable, direct-print, radiation-sensitive emulsion comprising gelatin, silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 100 mole percent based on said silver halide of a water-soluble iodide, and about .1 to 50 mole percent of Z-mercaptoimidazole based on said silver halide.

17. A light-developable, direct-print, radiation-sensitive emulsion comprising gelatin, silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 100 mole percent based on said silver halide of a water-soluble iodide, and about .1 to 50 mole percent of trimethylthiourea based on said silver halide.

18. A light-developable, direct-print, radiation-sensitive emulsion comprising gelatin, silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 100 mole percent based on said silver halide of a water-soluble iodide, and about .1 to 50 mole percent of l-(ortho-methoxyphenyl)-2-thiourea based on said silver halide.

19. A light-developable, direct-print, radiation-sensitive emulsion comprising gelatin, silver halide grains having an average size of about .1 to 10 microns, a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to 100 mole percent based on said silver halide of a water-soluble iodide, and about .1 to 50 mole percent of l-n-butyl-1,2,3,6-tetrahydro-1,3,5-triazine- 4-thiol based on said silver halide.

20. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns,

a predominant amount of the said radiation sensitivity being internal to said grains, about .1 to mole percent based on said silver halide of a substituted thiourea halogen acceptor having the formula R s R R I I(iI IR wherein:

(A) R and R are each selected from the group consisting of (1) a hydrogen atom,

(2) an alkyl group,

(3) an acyl group,

(4) an aryl group, and

(5) together the necessary atoms to complete a heterocyclic nucleus; and (B) R and R are each selected from the group consisting of (1) a hydrogen atom,

(2) an alkyl group,

(3) an acyl group, and

(4) an aryl group;

at least one of R R R and R being other than a hydrogen atom; and about .1 to mole percent based on said silver halide of a water-soluble halide salt selected from the group consisting of ammonium, calcium, lithium, magnesium, potassium and sodium bromide, chloride and iodide.

References Cited by the Examiner UNITED STATES PATENTS 1,995,444 3/1935 Berry 96-96 2,401,051 5/1946 Crouse et al. 96107 3,017,270 1/1962 Tregillus et al. 96-107 3,033,678 5/1962 Hunt 96119 3,033,682 5/1962 Hunt 96119 3,109,737 11/1963 Scott 96119 3,123,474 3/1964 Byrne 96108 OTHER REFERENCES Henney, et al.: Handbook of Photography, 1939, Me- Graw-Hill, page 462 relied on.

NORMAN G. TORCHIN, Primary Examiner. 

5. A LIGHT-DEVELOPABLE, DIRECT-PRINT, RADIATION-SENSITIVE EMULSION COMPRISING SILVER HALIDE GRAINS HAVING AN AVERAGE SIZE OF ABOUT .1 TO 10 MICRONS, A PREDOMINANT AMOUNT OF THE SAID RADIATION SENSITIVITY BEING INTERNAL TO SAID GRAINS, A HYDROPHILIC COLLOID, ABOUT .1 TO 50 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A MERCAPTAN HALOGEN ACCEPTOR HAVING AT LEAST ONE MERCAPTO GROUP ATTACHED TO A HETEROCYCLIC NUCLEUS HAVING AT LEAST ONE HETERO-NITROGEN ATOM, ABOUT .5 TO 120 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A CUPRIC SALT, ABOUT .1 TO 50 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A MERCAPTAN HALOGEN ACCEPTOR HAVING AT LEAST ONE MERCAPTO GROUP ATTACHED TO AN ARYL RADICAL,AND ABOUT .1 TO 50 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A WATER-SOLUBLE IODIDE.
 20. A LIGHT-DEVELOPABLE, DIRECT-PRINT, RADIATION-SENSITIVE GELATINO-SILVER HALIDE EMULSION COMPRISING SILVER HALIDE GRAINS HAVING AN AVERAGE SIZE OF ABOUT .1 TO 10 MICRONS, A PREDOMINANT AMOUNT OF THE SAID RADIATION SENSITIVITY BEING INTERNAL TO SAID GRAINS, ABOUT .1 TO 50 MOLE PERCENT BASED ON SILVER HALIDE OF A SUBSTITUTED THIOUREA HALOGEN ACCEPTOR HAVING THE FORMULA 